Is this corrosion

2nd505th

2nd505th

Pre-takeoff checklist
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2nd505th
DRnmWnd
Is this corrosion inside the aircraft wing? - if so is it too serious to deal with? What would you do to fix it?

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Looks like anticorrosion material, with the usual accumulation of dust and other grah-doo.

If so, you can clean it off with mineral spirits (or maybe lacquer thinner) and it should look shiny healthy aluminum underneath (prepare to re-coat that area otherwise it will be susceptible to corrosion).
 
I concur with Let’s go flying. Clean off a spot and see what’s underneath.
 
Looks like mold to me, try cleaning a small area with bleach and see if it comes off.
 
NO, NO NO, BLEACH!!! BLEACH HAS SODIUM HYDROXIDE AS A STABILIZER. IT WILL DISSOLVE ALUMINUM

Holy crap, bleach has to be the duct tape of chemicals.

And yes I am a degreed chemist. With decades in the aerospace industry.

REPEAT, NO BLEACH NEAR AIRCRAFT....NEVER...EVER...

Have a nice day
 
I think the big X's means your plane needs to be grounded.
 
Morgan3820 said:
NO, NO NO, BLEACH!!! BLEACH HAS SODIUM HYDROXIDE AS A STABILIZER. IT WILL DISSOLVE ALUMINUM

Holy crap, bleach has to be the duct tape of chemicals.

And yes I am a degreed chemist. With decades in the aerospace industry.

REPEAT, NO BLEACH NEAR AIRCRAFT....NEVER...EVER...

Have a nice day
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Didn't know that, but bleach does take out mold.
 
PaulS said:
Ah, so it would solve the problem forever.
Click to expand...

You got me there.
Actually, where I work this is an issue that we deal with that has no good remedy. Everything tried ends up attacking the structure, sooner or later.
 
Morgan3820 said:
NO, NO NO, BLEACH!!! BLEACH HAS SODIUM HYDROXIDE AS A STABILIZER. IT WILL DISSOLVE ALUMINUM
Click to expand...
Well, not quite. Consumer chlorine bleach is nothing more than a few percent Sodium Hypochlorite and water and is not particularly stable. I was going to write the chemical formula here but this board seems to not impelement the bbcode properly and it looked like crap when I wrote it out. Suffice it to say, even without Sodium Hydroxide added to the mix, dissolving Sodium Hypochlorite in water yields Sodium and Hydroxide ions as if you had added Sodium Hydroxide directly (it also release the hypochlorite ion which is what is doing the bleaching).
 
In other words, if you use bleach, if you don't have corrosion now, you will soon. Didn't know that though I've never been tempted to use bleach on aluminum.
 
flyingron said:
Well, not quite. Consumer chlorine bleach is nothing more than a few percent Sodium Hypochlorite and water and is not particularly stable. I was going to write the chemical formula here but this board seems to not impelement the bbcode properly and it looked like crap when I wrote it out. Suffice it to say, even without Sodium Hydroxide added to the mix, dissolving Sodium Hypochlorite in water yields Sodium and Hydroxide ions as if you had added Sodium Hydroxide directly (it also release the hypochlorite ion which is what is doing the bleaching).
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Just grabbed the Clorox SAs, "Lavender" bleach at random
https://www.thecloroxcompany.com/wp-content/uploads/2019/02/Clorox-Lavender-Bleach.pdf
It has 0.1 to 1% sodium hydroxide.

Secondly, the hydroxide ions you mention will corrode the aluminum- it doesn't matter if the source is the added sodium hydroxide, the disproportionation of sodium hypochlorite, or left over sodium hydroxide from making the bleach (on way to make it is to bubble chlorine gas through a sodium hydroxide solution).
 
Exactly. There's more hydroxide ions from the 3-6% NAOCl than the 1% NaOH. You don't want to use bleach.
 
Commercial bleach is manufactured by passing chlorine gas through 25% sodium hydroxide, which makes sodium hypochlorite:

Cl2 + 2 NaOH --> NaOCl + NaCl + H2O
​
This solution is diluted to a final concentration of just over 5% NaOCl, and is strongly alkaline from excess NaOH (around pH 11). Alkali will destroy (dissolve) aluminium while generating hydrogen gas. It belongs nowhere near aluminum aircraft.
 
Morgan3820 said:
Well, consumer bleach is made by diluting industrial strength sodium hypochlorite which is made by reacting chlorine with sodium hydroxide.
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Which means absolutely nothing really. It just shows that the NaOCl was made up from NaOH and Cl2. As pointed out the issue is (even without any added NaOH) that NaOCl will dissassociate into -OH ions just as if you'd added NaOH directly.
 
flyingron said:
Exactly. There's more hydroxide ions from the 3-6% NAOCl than the 1% NaOH. You don't want to use bleach.
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OCl− + H2O ⇌ HOCl + OH−
It depends on the equilibrium constant for that reaction. The addition of the hydroxide tends to keep it shifted to the left. That 1% of added sodium hydroxide is sufficient to keep the equilibrium shifted to the left.
 
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I wonder if the OP is still with the tread?

I Didn’t know that there were other chemists active on the forum
 
flyingron said:
Which means absolutely nothing really. It just shows that the NaOCl was made up from NaOH and Cl2. As pointed out the issue is (even without any added NaOH) that NaOCl will dissassociate into -OH ions just as if you'd added NaOH directly.
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And the added hydroxide ions (~1% sodium hydroxide) shift the equilibrium to the left as per Le Chatelier’s Principle.
 
Cap'n Jack said:
OCl− + H2O ⇌ HOCl + OH−
It depends on the equilibrium constant for that reaction. The addition of the hydroxide tends to keep it shifted to the left. That 1% of added sodium hydroxide is sufficient to keep the equilibrium shifted to the left.
Click to expand...

The Kb for OCl- dissociation is around 10^-6, enough to produce a pH of 10-11 at 5% NaOCl by weight. There is also some additional excess NaOH in the solution to stabilize OCl- from excessive disproportionation back into chlorine gas and bubbling away. No matter how you slice it, bleach solution is terribly alkaline and destructive to aluminum.
 
chemgeek said:
The Kb for OCl- dissociation is around 10^-6, enough to produce a pH of 10-11 at 5% NaOCl by weight. There is also some additional excess NaOH in the solution to stabilize OCl- from excessive disproportionation back into chlorine gas and bubbling away. No matter how you slice it, bleach solution is terribly alkaline and destructive to aluminum.
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So... that's roughly about about 1% solution of NaOH (not counting the added sodium hydroxide). The equilibrium is generally shifted towards the left.

We all agree, at least, bleach is terrible for cleaning aluminum. The rest is just fine details.
 
chemgeek said:
Commercial bleach is manufactured by passing chlorine gas through 25% sodium hydroxide, which makes sodium hypochlorite:

Cl2 + 2 NaOH --> NaOCl + NaCl + H2O
​
This solution is diluted to a final concentration of just over 5% NaOCl, and is strongly alkaline from excess NaOH (around pH 11). Alkali will destroy (dissolve) aluminium while generating hydrogen gas. It belongs nowhere near aluminum aircraft.
Click to expand...

My mother always said it was considered uncouth to pass gas. I told her it was just another example of better living through chemistry.
 
Morgan3820 said:
I wonder if the OP is still with the tread?

I Didn’t know that there were other chemists active on the forum
Click to expand...

My bio/chem degree hasn’t been used in 35 years but it still is interesting looking back at what I once knew.
 
1RTK1 said:
My bio/chem degree hasn’t been used in 35 years but it still is interesting looking back at what I once knew.
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My Daughter is her second year for a biochemistry degree. It is getting harder to help her with her homework assignments.
 
NordicDave said:
Just make sure the bleach is mixed with equal parts ammonia.

(Joke)
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this is starting to sound like things I aspired to when 14! Anything to cause a violent reaction or better yet, blow stuff up! Doesn't your combo produce rocket fuel?
And with vinegar instead, the chance to suffocate yourself with toxic fumes?
 
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